Three situations are typically encountered in the connection and disconnection of electrical connectors in power distribution systems. The so-called "loadmake" situation involves the joinder of male and female contact elements, one energized and the other engaged with a normal load. An arc of moderate intensity is struck between the contact elements as they approach one another and until joinder. The so-called "loadbreak" situation involves the separation of such mated male and female contact elements, while they supply power to a normal load. Moderate intensity arcing again occurs between the contact elements from the point of separation thereof until they are somewhat removed from one another. The so-called "fault closure" situation involves the joinder of male and female contact elements, one energized and the other engaged with a load having a fault, e.g., a short circuit condition. Quite substantial arcing occurs between the contact elements as they approach one another and until joinder, giving rise to the possibility of explosion and accompanying hazard to operating personnel.
Prior art efforts have reached a point wherein arcing in the loadmake and loadbreak situations is accommodated to more than a satisfactory extent. Thus, connector assemblies in wide-spread use employ materials which emit arc-quenching gas when subjected to arcing, thereby adequately dissipating the moderate intensity arcs occurring in these situations. Arcing in the load-break situation may be accommodated even further by connector assembly structure providing for operator movement of the contact elements, while mated, until the female contact element abuts against a stop member and the male contact element separates therefrom at high velocity as disclosed in Rueffer U.S. Pat. No. 3,259,726 and Kotski U.S. Pat. No. 3,542,986.
Devices not employing the above-mentioned high velocity contact separating structure for loadbreak accommodation, but suited for use in all three situations are shown in Ruete et al. U.S. Pat. No. 3,539,972 and Brown U.S. Pat. No. 3,654,590, commonly-assigned herewith.
As respects the fault closure situation, certain prior art efforts have looked to the use of the aforementioned arc-quenching gas for assistance in accelerating contact elements into engagement. While such prior art gas-assisted contact element engagement efforts have proved advantageous, need exists for continued improvement in connectors relying on arc-quenching gas-assistance in accommodating the fault closure situation through accelerated contact element engagement. Those prior art measures involving arc-quenching gas-assisted contact element movement are now discussed with particularity.
In Whitney U.S. Pat. No. 1,955,215 and in the above-mentioned Kotski U.S. Pat. No. 3,542,986, male and female contact elements having an arc-quenching guide in the latter patent, are joined in accelerated manner by the assistance of gas pressures attending arcing. In these efforts, an open-ended female contact element is supported by an open-ended piston movable in an axial passage in the connector housing. Arc-quenching gas is said to be conducted, without restriction, through the female contact element to exert net pressure on the piston. The piston and hence the female contact element are accordingly displaced in the direction of the male contact element, facilitating joinder more rapidly than would otherwise occur in the absence of such displacement. In freely conducting arc-quenching gas throughout the continuous volume of a female contact and a piston, these prior art efforts effect fault closure at the cost of less than desired loadbreak performance, since in loadbreak performance, it is desirable that the arc-quenching gas be restricted to a confined volume to facilitate containment of such conductive gas in the contact region upon contact separation.
In still another arrangement in present use and described in Joy Manufacturing Company Bulletin 215-4, January 1972, a connector housing includes an axial passage and fixedly supports therein a female contact element defining a chamber for receiving arc-quenching gas. The housing defines a cavity and includes a valve closing one end of the female contact element and thereby separating the female contact element chamber from the housing cavity. A piston disposed in the housing passage encircles the fixed female contact element and is in sliding engagement therewith. The piston supports an arc-quenching guide and a ring-shaped contact element for joint movement therewith. The ring-shaped contact element engages the male contact element on its insertion in the housing at a time prior to joinder thereof with the fixed female contact element. Arc-quenching gas generated by the arc struck between such ring contact and the male contact element during fault closure is conducted into the fixed female contact element chamber and operates the valve, the gas thereupon entering the cavity and moving the piston toward the male contact element. Prior to ultimate engagement of the male and female contact elements, fault current flows through the ring-shaped contact element and is transferred to the female contact element through sliding frictional engagement thereof with the piston. This arrangement is less than desirable in that circuit resistance varies widely during fault closure due to its dependence on indeterminate sliding frictional engagement between the piston and the female contact element surfaces. Furthermore, since the female contact element is fixed in the housing, and since the ring-shaped contact element does not frictionally engage the male contact element, this Joy device does not involve the aforementioned Rueffer patent loadbreak assist, and accordingly effects accelerated fault closure at the cost of less than desired loadbreak performance.